This invention is particularly applicable to fluidic catalytic cracking units (FCCU) of the type having a perforated distributor grid floor which is hereinafter referred to as a grid floor. The grid floor supports a fluidized catalyst bed in a catalyst regenerator vessel. It is necessary, in the catalyst regeneration process, to distribute air evenly throughout the fluidized catalyst bed in the regenerator vessel. This is accomplished by uniformly passing air upwardly through the grid floor of the regenerator vessel such that the air is evenly distributed throughout the fluidized catalyst bed. The grid floor must be sealed relative to the vessel wall, otherwise air passing in a gap between the floor and the vessel wall can create hot spots in the fluidized catalyst being regenerated and can ultimately result in a shut-down of the FCCU.
The interior of an FCCU regenerator containing the fluidized catalyst operates at a high temperature which causes the grid floor to expand and contract several inches between start-up and shut-down, while there is relatively little or no change in the diameter of the insulated regenerator wall. Also there are other effects which encourage by-passing of air and other regenerator gases around the edge of the grid floor, such as tendencies toward deformation of the grid floor and the vessel wall due to differential expansion, and the erosive effects of the fluidized catalyst which moves within the vessel.
Accordingly, it is an object of this invention to provide a method to prevent passing of gases around the grid floor of a catalyst regeneration vessel.
It is a further object of this invention to provide apparatus for providing a seal between the grid floor and the vessel wall in a catalyst regeneration vessel.